Unerupted teeth cannibalizing their neighbors: part 2

Published: April 2016

Bulletin #54 April 2016

Unerupted teeth
cannibalizing their neighbors: part 2

In part 1 of the article, which
appeared as the March 2016 bulletin #53 on this website, I discussed the
resorptive process that affects the roots of teeth adjacent to and initiated by
an impacted tooth, particularly a maxillary canine which had “lost its sense of
direction” while still exercising eruptive potential. Since the canine is the
most frequently seen example of this phenomenon, the present discussion will
largely relate to it, although the principles are the same for other teeth. In the
conclusion to the March 2016 bulletin I noted that, when the resorption has
penetrated into the pulp, a merging
of the resorptive soft tissue of the periodontium and the pulp occurs which is
entirely free of bacteria, free of surgical trauma and, in consequence, free of
inflammation. The
dental pulp is healthy, vital and symptomless and the natural color of the tooth
is unchanged ………….. and, because there is no pathology, no
treatment is indicated, i.e. neither root canal treatment, nor surgical
apicoectomy, nor extraction! It was also pointed out that, once
the aberrant canine is distanced from the immediate area, the resorption
abruptly ceases, as we have demonstrated in clinical research carried out in
Jerusalem.1

Obviously, then, this phenomenon should
be the first and most urgent priority to be addressed in the orthodontic
treatment with the aim of preserving as much of the root of the tooth as
possible. It should precede all other goals of the orthodontic treatment,
including relegating the essential orthodontic opening of space in the arch for
the canine to second place.

We now pick up the narrative again, after the danger of
losing the resorbed tooth and the impacted tooth has largely receded and move
on to the more routine part of the orthodontic treatment, i.e. to align the
other teeth in both jaws and to achieve good occlusal relations, with appropriate
follow-up. Aside from the observations and conclusions referred to in last
month’s bulletin, several new questions arise that need to be addressed.

Fig. 1a. Anterior section of the
maxilla depicted on a panoramic film showing 2 unerupted permanent canines. The
left canine is associated with marked resorption of the root of both the
central and lateral incisors.

Fig. 1b. A cross-sectional frame
from the CBCT to show the severity of the oblique labial resorption of the root
of the lateral incisor.

Question 1: How can a surgeon
expose the impacted tooth, without devitalizing the adjacent tooth?

As with any impacted tooth, the use of radiographic imaging
for accurate positional diagnosis and for searching the immediate area for additional
pathology is of extreme importance before embarking on treatment of this
anomaly (Fig. 1a, b). In the present context, a cone beam CT should be
considered mandatory. It is logical that a labial canine needs to be exposed
from the labial side and orthodontic traction similarly directed, while a
palatal canine needs to be exposed and traction applied from the palatal
aspect. However, there are a good number of impacted canines that are located
within a progressively enlarging apical resorption crater of the incisor root.
The lip of this crater may be higher on one side than on the other and this may
determine which way the tooth should best be directed to resolve the impaction.

Fig. 1c, d. Together with extraction
of the first premolar tooth, a full labial flap has been raised from the
attached gingiva at the necks of the incisors. Only the incisal part of the
crown of the canine is exposed for bonding of the eyelet attachment and the
lingual aspect of the tooth, adjacent to the resorbed root of the incisor,
remains untouched.

Having determined on which side to perform the exposure, my
recommendation for the surgery in these difficult cases is to raise a broad,
full-thickness flap from the attached gingiva around the necks of the teeth and
to extend it superiorly by blunt dissection, to reveal the underlying bone. The
impacted canine is beneath the surface that is exposed by the surgeon. It
comprises a very thin shell of bone which bulges the flat surface of the bony
profile and is often not visible radiographically. Using the various
radiographic and CT images as guides, the exact location of the crown of the
tooth and of the resorption front must be accurately determined on the exposed
bony surface.The thin bony cover is then
perforated over the crown of the tooth, as far away from the resorption front
as possible to expose the dental follicle. An opening in the follicle is made
which requires to be widened enough to expose a minimum of enamel surface,
enough for the orthodontist to bone a small eyelet attachment (Fig. 1c, d). Because the
surgeon is on hand to maintain control of bleeding, using a fine canula
attached to the suction system, this entire surgical procedure may be
accomplished with remarkably little surgical trauma.

Fig. 2a. An auxiliary labial
archwire is ligated into the brackets “piggy-back style” over a heavy main arch
with the loop in its horizontal passive mode, prior to the surgery. A full soft
tissue flap has been raised from the attached gingiva of the deciduous canine
and permanent incisors adjacent to the impacted right canine, which is located
high above the resorbed root of the central incisor.

Fig. 2b. The twisted steel ligature
from the bonded eyelet attachment is threaded through the terminal helix of the
auxiliary archwire.

Fig. 2c. The loop of the auxiliary
archwire is turned upward under light finger pressure and secured by turning
over the twisted ligature to hold it against the re-sutured flap in its active
mode. A small ball of composite material is cured over the helix and ligature
to present a smooth and comfortable extremity to avoid ulceration of the oral
mucosa.

The full flap must be sutured back to its former place to
re-cover the tooth and the newly bonded eyelet. The twisted steel ligature that
was tied into the eyelet of the attachment is taken through a pierced needle
hole or slit in the middle of the sutured flap, opposite the location of the
tooth beneath. In this way, the orthodontist will have the opportunity to apply
traction to the tooth immediately, by tying a custom-made spring or elastic
thread to the ligature. The initial activation is done before the patient is
discharged from the operatory and while the area is still anesthetized, both
for a labial canine (Fig. 2a-c) and for a palatal canine (Fig. 3a-f).

Fig. 3a. A full palatal flap is
reflected from the gingival margins of the adjacent teeth to reveal the palatal
side of the canine, which is very close to the root of the lateral incisor.
Note the presence of an auxiliary archwire with a vertical loop in its passive
mode, overlying the rectangular base archwire, having been placed immediately
prior to the surgery.

Fig. 3b. An eyelet attachment is
place on the palatal side.

Fig. 3c. The full flap is re-sutured
back to its former place, with the twisted connector ligature exiting through
the palatal mucosa.

Fig. 3d. The vertical loop of the
auxiliary archwire is pushed palatally and upwards to be ensnared into its
active horizontal mode in the shortened connector, which is turned into a hook.
The active force is vertically directed.

Fig. 3e, f. Two months later, the
canine has erupted away from the lateral incisor and a new eyelet is
substituted on the anatomically labial aspect of the canine for direct elastic
traction to the archwire.

It should be abundantly clear that an open surgical
procedure should be avoided, since the crown of the impacted tooth cannot be
exposed adequately without also exposing the root of its neighbor, if one is to
ensure that it will not close over within a few days post-operatively. When the
impacted tooth is located directly in the actively resorbing apical section,
any open procedure is likely to cause a loss of vitality of the resorbed tooth.

Question 2: After the canine has been distanced and the
resorption has stopped, is moving the affected tooth a viable option or will
this re-kindle the resorption process?

The etiology of this form of
resorption is concerned with the proximity of the impacted tooth and its potential
for eruptive movement. Following the distancing of the impacted tooth,
therefore, there is no reason to suspect further resorption from this cause.
Nevertheless, resorption occurs from other causes during orthodontic movement
of a tooth, particularly the arguably predictable orthodontically induced
inflammatory root resorption (OIIRR),2. but also others.3However, these are generally insignificant
and, if the further movement of the tooth is kept to an acceptable minimum,
there is no reason to suspect further danger to the tooth.

In part 1 of this article, I
asked how the oral surgeon, the periodontist, the endodontist and the pediatric
dentist would view the above scenario and whether they might advise treatment
for the problem created by this variety of root resorption. Now let’s ask what the orthodontist would or
should do?

Question 3: Should the
orthodontist “dare” to move the tooth or should he/she be frightened of being
sued if, perchance, the tooth were to be further compromised and possibly lost
during the treatment?

In these cases, the parent must
be brought into the discussion and informed of the problem together with the
options for treatment. The parent should be advised, at the outset, that there
is a danger that the tooth may be lost and the decision to nevertheless attempt
orthodontic resolution should be made together with the parent. A signed
statement to that effect should be elicited from the parent.

During the period of active
root resorption, the immediate area of alveolar bone is rarified and this
appears on a radiograph as a dark radiolucency. The tooth itself exhibits a
marked degree of mobility, depending on how much of the root has been lost. While
the impacted tooth is being moved away from the immediate area, the resorbed
tooth must be treated with great care. It should not be used as a supportive
element for the orthodontic appliance or a counter balance to forces exerted
elsewhere. With certain exceptions, the tooth should not carry a bracket or be
tied into the orthodontic scheme until much later.

In the weeks and months that
follow, the resorbed tooth becomes much firmer and this is related to the
deposition of new bone in the apical area which can be easily seen on a routine
periapical film. However, given the reduced root length, correspondingly
reduced forces should be used in order to keep the force per unit of root
surface to a physiologic level. Towards the end of the overall orthodontic
treatment, the resorbed tooth can be included into the general appliance scheme
and reasonable orthodontic forces applied to move it into the desired position,
including root uprighting and torqueing vectors. Optimal rather than ideal
finishing procedures should be the rule.

Fig. 4a. This is the completed
result of the case illustrated in Fig. 1a-d. The quality of the periodontium on
the treated (left) side and its appearance compare favorably with those of the
normally erupted canine of the opposite side.

Fig. 4b. Periapical views of the
anterior teeth shows the shortening of the root of the left central incisor.
The severe oblique resorption of the entire labial side of the root of the
lateral incisor is represented on this film as thin, indistinct and radiolucent, but almost full length.

Question 4: At the completion of treatment, will it be
possible to achieve a result in which the appearance can be made
indistinguishable from the teeth on the
other side and where periodontic parameters are in the range of normal?

Since the resorbed incisor will be of normal shape and
color, the likelihood of achieving a good appearance are very good. If the
impacted tooth has been erupted through attached gingiva, its periodontic
parameters will be close to ideal (Fig. 4a).

Fig. 5a. A right labial canine has
been drawn through the oral mucosa, high in the vestibulum.

Fig. 5b. Reparative periodontal
surgery was not performed and the result shows the long clinical crown of the
canine invested with labial oral mucosa. The unaffected canine of the unaffected left side is invested with mildly inflamed but attached gingiva.

On the other hand, if a labially impacted
tooth has been erupted through the oral mucosa, without any modifying surgical
procedure being undertaken to obviate it (Fig. 5a), the periodontal tissue that
invests the labial side of the tooth in the final instance will be very thin,
mobile and red and the clinical crown will be elongated in comparison with an
opposite unaffected side (Fig. 5b). The non-keratinized mucosal tissue will
ulcerate easily in function and during simple oral hygiene procedures.

Question 5: At the completion of treatment, will it be
possible to achieve a result in which the prognosis of the affected tooth is
equivalent to that of the unaffected tooth on the other side, or at least, that
it may last long enough to pose as a medium term stop-gap until the child’s
general growth has ceased and an artificial implant-borne replacement can be
advised?

Fig. 6a. A case with severe root
resorption of both maxillary lateral incisors due to impaction of the canines,
seen here in May 1999.

Fig. 6b. The same case on the day
appliances were removed, in June 2002. There is a good height of alveolar
crestal bone, which provides no more than a millimeter or two of support for
the severely resorbed lateral incisors.

Fig. 6c. The same case at follow-up
5.6 years later, in December 2007, with a twistflex bonded retainer in place.
Note the vertical increase in bony support, consolidation of bone and good
trabecular pattern around the stunted root ends.

Unless the remaining portion of the root of the tooth is
very short indeed, the prognosis of the tooth will be good and may last for
many years, possibly as long as many of the other neighboring teeth1.
In the event that the root of the tooth is very truncated, with no more than a
millimeter or two of alveolar bone support, splinting the tooth with a lingual
bonded twistflex type of retainer will eliminate mobility and usually
permit the retention of the tooth into adulthood (Fig. 6a-c).

Fig. 7a. The left lateral incisor
has lost almost its entire root to resorption.

Fig. 7b. The clinical intra-oral
view of the anterior dentition shows the shallow concavity in the profile of
the alveolar process of the atrophic edentulous area corresponding to the area
where resorption of the root has occurred (arrow).

Question 6: Will the form of the alveolar ridge in the
immediate area be normal?

New alveolar bone accompanies the eruption of teeth,
whether following natural or mechanically-encouraged eruption. Thus, from this
standpoint the bone height will undoubtedly be increased to the level of the
interproximal bone linking the adjacent teeth. However, within a short time
after completion of treatment, the surface profile of the area above the tooth
will often feature a shallow concavity (Fig. 7a, b), corresponding to the area
where one would normally expect to see the outline of the missing incisor root.
So, the vertical height of the alveolus is normal and its width in the area of
the cervical margin of the tooth will be similarly normal. However, in the area
corresponding to the loss of root, it will become bucco-lingually very narrow,
since this will have effectively turned into an atrophic edentulous area.